There is a ton of work looking at BOLD functional connectivity (FC) in Alzheimer’s Disease, and one consensus that has emerged is that this is a disconnection syndrome, with most studies finding weaker connectivity within the default mode network (DMN), including connectivity to DMN cortex from the hippocampus and/or MTL. But what happens inside the MTL ? There is intricate feedback circuitry within the MTL, highlighted by the perforant path that connects extra-hippocampal cortex to the hippocampus. Thanks to our automated MTL subregion labeling technique (implemented in the publicly available ASHS software), we are in a position to carefully label MTL subregions and measure connectivity between these. That’s what we did in a paper published in Hippocampus last year. This work was in collaboration with David Wolk at the Penn Memory Center.
This figure summarizes the findings. We found increased FC of MTL subregions to Entorhinal cortex (one of the first areas to show tangle pathology in the disease) in prodromal AD patients, but also evidence of the aforementioned, widely reported disconnection between MTL and neocortex.